How to Identify and Resolve UTF-8 Character Encoding Mismatches?

UTF-8 Character Encoding Mismatches: Identifying and Resolving Issues

Overview

Working with UTF-8 character sets can pose challenges when managing text data. This article explores the various issues that can arise and provides solutions to help resolve them.

Problem Symptoms

• Unexpected characters: Asian characters appearing as ???? or characters like "Señor" appearing as "Se?or".
• Mojibake (gibberish): Strange characters such as "Señor" or "新浪新闻" for "新浪新闻".
• Black diamonds: Characters displayed as black diamonds with question marks, e.g., "Se�or".
• Truncated data: Loss or truncation of characters, e.g., "Se" instead of "Señor".
• Incorrect sorting: Data not sorting correctly even when it appears visually correct.

Causes and Solutions

Truncated Data:

• Ensure that the data to be stored is encoded as UTF-8mb4.
• Verify that the connection during both writing and reading is using UTF-8/UTF-8mb4.

Black Diamonds:

• Case 1 (original bytes not UTF-8): Encode the data as UTF-8 and ensure the connection (or SET NAMES) is set to UTF-8/UTF-8mb4 during both insertion and selection. Verify that the database column is CHARACTER SET UTF-8 (or UTF-8mb4).
• Case 2 (original bytes were UTF-8): Check that the connection during selection is set to UTF-8/UTF-8mb4 and verify the database column's character set.

Question Marks:

• Encode the data as UTF-8/UTF-8mb4.
• Set the database column's character set to UTF-8 (or UTF-8mb4).
• Ensure that the connection used during data retrieval is UTF-8.

Mojibake/Double Encoding:

• Encode the data as UTF-8.
• Set the connection during insertion and selection to UTF-8/UTF-8mb4.
• Declare the database column as CHARACTER SET UTF-8 (or UTF-8mb4).
• Use in HTML.

Incorrect Sorting:

• Choose the appropriate collation that matches your sorting requirements.
• Rule out double encoding issues by checking that the HEX of the characters corresponds to the expected UTF-8 encoding.

Data Recovery

• In cases of data truncation or loss, the data is generally unrecoverable.
• For other issues (e.g., mojibake/double encoding, black diamonds), follow the fixes outlined above to recover the data.

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